As aging or degradation will incur in a battery pack after the battery pack has been used for a long period of time, it is necessary to estimate a state of health (SOH) of the battery pack. Usually, the state of health of the battery pack, which is estimated based on a cumulative change in capacity of the battery pack, is represented as SOHC. Prior methods for estimating the SOHC of the battery pack have the following disadvantages:
In an aspect, during normal use of an electrical system, for example, an electric vehicle powered by the battery pack, the electrical system does not have an opportunity to accurately calculate the SOHC of the battery pack.
In another aspect, states of charge (SOCs) of different batter units in the battery pack are inconsistent with each other, and it is difficult to calculate the SOC of a specific battery unit.
In yet another aspect, aging processes of respective battery units in the battery pack are inconsistent with each other, so the SOHC of a whole of the battery pack cannot reflect actual aging states of respective battery units.
For the above reasons, the prior methods for estimating the SOHC of the battery pack cannot obtain an accurate SOHC of the battery pack.